During photosynthesis, at low sunlight intensities, all absorbed photons are utilized efficiently to drive electrons in the electron-transport chain. As the level of irradiance increases further, photosynthesis becomes saturated and reaches a plateau due to the fact that the carbon reactions cannot keep up with the linear increase in light absorption. Plant lines with a wild type light-harvesting antenna system reach this light intensity for saturation at lower levels of irradiance than their mutant counterparts. The sunlight harvested by the chlorophyll antenna exceeds the maximal operational capacity of the electron-transport chain and of the carbon reactions of photosynthesis, rendering the excess absorbed photons useless. Under bright sunlight conditions (2500 μmol photons m-2 s-1), wild type lines with their fully developed light-harvesting antenna utilize photons inefficiently; only about 20% of the incoming sunlight energy is converted into useful photosynthesis, while excess absorbed energy is dissipated by the non-photochemical quenching (NPQ) process.